1. Field of the Invention
Embodiments of the present invention relate to a method and apparatus for delivery of one or more reactants to a substrate processing chamber. More particularly, embodiments of the present invention relate to a valve assembly for rapid delivery of pulses of one or more reactants to a substrate processing chamber.
2. Description of the Related Art
Reliably producing sub-micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large scale integration (ULSI) of semiconductor devices. However, as the fringes of circuit technology are pressed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on the processing capabilities. The multilevel interconnects that lie at the heart of this technology require precise processing of high aspect ratio features, such as vias and other interconnects. Reliable filling of the interconnects is important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates.
As circuit densities increase, the widths of vias, contacts, and other features, as well as the dielectric materials between them, decrease to sub-micron dimensions (e.g., less than 0.20 micrometers or less), whereas the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increase. Many traditional deposition processes have difficulty filling sub-micron structures where the aspect ratio exceeds 4:1, and particularly where the aspect ratio exceeds 10:1. Therefore, there is a need for technology that provides for the formation of substantially void-free and seam-free sub-micron features having high aspect ratios.
Atomic layer deposition is one deposition technique being explored for the deposition of material layers into high aspect ratio vias. An atomic layer deposition (ALD) process is a cyclical deposition method that is generally used for depositing ultra-thin layers (e.g., mono-layers) over features of semiconductor devices having a high aspect ratio.
One example of atomic layer deposition comprises the sequential introduction of pulses of gases. The ALD process utilizes a chemisorption phenomenon to deposit mono-layers of reactive precursor molecules. During the ALD process, reactive precursors are injected, in the form of pulsed gases, into a deposition chamber in a predetermined cyclical order. Each injection of a precursor provides a new atomic layer on the substrate that is additive to or combines with the previously deposited layers. Injections of individual precursor gases generally are separated by injections of a purge gas. In some instances, the purge gas may be flown continuously into the deposition chamber. The purge gas generally comprises an inert gas, such as argon (Ar), helium (He) and the like, or a mixture thereof. During the ALD process, the deposition chamber is also continuously evacuated to reduce the gas phase reactions between the precursors.
By way of example, during an ALD operation a first cycle for the sequential introduction of pulses of gases may comprise a pulse of a first reactant gas, followed by a pulse of a purge gas and/or a pump evacuation, followed by a pulse of a second reactant gas, and followed by a pulse of a purge gas and/or a pump evacuation. The term “gas” as used herein is defined to include a single gas or a plurality of gases. Sequential introduction of separate pulses of the first reactant and the second reactant may result in the alternating self-limiting adsorption of monolayers of the reactants on the surface of the substrate, thus forming a thin layer of material for each cycle. The cycle may be repeated to a desired thickness of the deposited material.
Various problems exist with current gas delivery apparatuses used to perform atomic layer deposition. Examples include slow delivery of reactants, generation of particles, and/or failure over time of components of the gas delivery apparatuses. Therefore, there is a need for new apparatuses and methods to perform gas delivery, such as during an ALD procedure.